The invention generally relates to electric motors and, more particularly, the invention relates to electric motors with multiple stators.
Rotational torque in an electric motor typically is improved when multiple stators are utilized to rotate a common rotor. Such motors generally are referred to as xe2x80x9cmulti-statorxe2x80x9d motors. Each stator in a multi-stator motor typically includes poles and windings that are selectively energized by shared energizing circuitry. Energizing circuitry typically includes magnetic sensors (e.g., Hall effect sensors) to detect the rotational position of the rotor, switching circuitry to alternatively energize the windings and poles of selected stators, voltage regulation circuitry for regulating input voltage, and current limiting circuitry (e.g., a fuse) for limiting input current into the motor.
Problems arise, however, when the energizing circuitry malfunctions. For example, the voltage regulation circuitry may malfunction, consequently not providing enough energizing voltage to the windings. Accordingly, the motor undesirably may not operate since the windings cannot be energized. Other similar energizing circuitry malfunctions also can cause the motor to stop functioning. It therefore would be desirable to have energizing circuitry on an electric motor that enables the motor to continue operating even if such circuitry does malfunction.
In accordance with one aspect of the invention, first and second stator circuitry for respective use with first and second stators in a multi-stator motor are configured so that, when operating, the first stator circuitry will continue to energize a first winding in the first stator even when the second stator circuitry fails to energize a second winding in the second stator. To that end, the motor includes a rotor that rotates through a plurality of rotational positions, the first stator having the first stator circuitry and the first winding, and the second stator having the second stator circuitry and the second winding. The first stator circuitry energizes the first winding in response to the rotational position of the rotor. In a similar manner, the second stator circuitry energizes the second winding in response to the rotational position of the rotor.
In other embodiments of the invention, the operation of the second stator circuitry is substantially unaffected by a failure of the first stator circuitry to energize the first winding. The first stator circuitry may include means for receiving power from a first power source, while the second stator circuitry may include means for receiving power from a second power source. Failure of one power source therefore does not affect the performance of the stator utilizing the other power source.
In yet other aspects of the invention, the first stator circuitry includes a first voltage regulator for regulating input voltage into the first stator circuitry, and a first current limiter for limiting input current into the first stator circuitry. In a similar manner, the second stator may include a second voltage regulator for regulating input voltage into the second stator circuitry, and a second current limiter for limiting input current into the second stator circuitry. In preferred embodiments, the first stator and the second stator are substantially concentric. In other embodiments, the first stator is angularly offset from the second stator. The first stator also may include a first pole that contacts the second winding, thus reducing the profile of the motor. In yet other embodiments, the rotor may include an impeller.
In another aspect of the invention, the first stator circuitry is substantially independently operable from the second stator circuitry. Specifically, the first stator circuitry may be considered to be electrically independent from the second stator circuitry.